Try to avoid codecov spam.

I am increasing the threshold even more for when
codecov complains.  Since the tool reports so many
false negatives, we should probably change our philosophy
on code coverage so that this tool only reports
catastrophic commits (like .e.g. a commit that prevents
running a whole test suite) and let our more specific
tools continue to catch things like regressions of files
from 100% coverage.

.codecov.yml

@@ -5,6 +5,6 @@ coverage:
     project:
       default:
         target: auto
-        threshold: 0.07
+        threshold: 0.50
         base: auto
     patch: off